I'm not really sure how to express it but I'm searching for unicode letters which are more than one visual latin letter.

I found this in Word so far:

• DZ
• Dz
• dz
• NJ
• Lj
• LJ
• Nj
• nj

Any others?

Here are some of the characters I've found. I'd first done this manually by looking at some probable blocks. However I've later written a Python script to do this automatically that you can find at the end of this answer

Digraphs

Ligatures

There are a few other ligatures that are used for phonetic transcription but looks like Latin characters

https://en.wikipedia.org/wiki/List_of_precomposed_Latin_characters_in_Unicode#Digraphs_and_ligatures

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Edit:

There are more letterlike symbols beside ℻ and ℡ like what the OP found in the comment:

℀ ℁ ⅍ ℅ ℆ ℔ ℠ ™

Longer letters are mainly from the CJK Compatibility block

Among the 3-letter-like symbols are ㎈ ㎑ ㎒ ㎓ ㎔㏒ ㏕ ㏖ ㏙ ㎪ ㎫ ㎬ ㎭ ㏆ ㏿ ㍱... Probably the ones with most characters are ㎉ and ㎯

Unicode even have codepoints for Roman numerals. Here another 4-letter-like character can be found: Ⅷ

If normal numbers can be considered then there are some other code points for multiple digits like ⒆ ⒇ ⓳ ⓴ in enclosed alphanumerics

and in Enclosed Alphanumeric Supplement

🅫, 🅪, 🆋, 🆌, 🆍, 🄭, 🄮, 🅊, 🅋, 🅌, 🅍, 🅎, 🅏

A few more:

Currency symbol group

₧ ₨ ₶ ₯ ₠ ₢ ₷

Miscellaneous technical group

⎂ ⏨

Control pictures (probably you'll need to zoom out to see)

Alchemical Symbols

🜀 🜅 🜆 🜇 🜈 🝪 🝫 🝬 🝛 🝜 🝝

Musical Symbols

𝄶 𝄷 𝄸 𝄹 𝄉 𝄊 𝄫

And there are the emojis 🔟 💤🆔🚾🆖🆗🔢🔡🔠 💯🆘🆎🆑™🔙🔚🔜🔝🔛📆🗓🔞

Vertical bars may be considered uppercase i or lowercase L (like your 〷 example which is actually the TELEGRAPH LINE FEED SEPARATOR SYMBOL) and we have

• Vai syllable see ꔖ 0xa516
• Large triple vertical bar operator ⫼ 0x2afc
• Counting rod tens digit three: 𝍫 0x1d36b
• Suzhou numerals 〢 〣
• Chinese river 川
• ║ BOX DRAWINGS DOUBLE VERTICAL...

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Here's the automatic script to find the multi-character letters

import unicodedata

for c in range(0, 0x10FFFF + 1):
    d = unicodedata.normalize('NFKD', chr(c))
    if len(d) > 1 and d.isascii() and d.isalpha():
        print("U+%04X (%s): %s\n" % (c, chr(c), d))

It won't be able to find many ligatures like æ or œ because they're not considered orthographic ligatures and aren't decomposable in Unicode. Here's the result in Unicode 11.0.0 (checked with unicodedata.unidata_version)

U+0132 (IJ): IJ
U+0133 (ij): ij
U+01C7 (LJ): LJ
U+01C8 (Lj): Lj
U+01C9 (lj): lj
U+01CA (NJ): NJ
U+01CB (Nj): Nj
U+01CC (nj): nj
U+01F1 (DZ): DZ
U+01F2 (Dz): Dz
U+01F3 (dz): dz
U+20A8 (₨): Rs
U+2116 (№): No
U+2120 (℠): SM
U+2121 (℡): TEL
U+2122 (™): TM
U+213B (℻): FAX
U+2161 (Ⅱ): II
U+2162 (Ⅲ): III
U+2163 (Ⅳ): IV
U+2165 (Ⅵ): VI
U+2166 (Ⅶ): VII
U+2167 (Ⅷ): VIII
U+2168 (Ⅸ): IX
U+216A (Ⅺ): XI
U+216B (Ⅻ): XII
U+2171 (ⅱ): ii
U+2172 (ⅲ): iii
U+2173 (ⅳ): iv
U+2175 (ⅵ): vi
U+2176 (ⅶ): vii
U+2177 (ⅷ): viii
U+2178 (ⅸ): ix
U+217A (ⅺ): xi
U+217B (ⅻ): xii
U+3250 (㉐): PTE
U+32CC (㋌): Hg
U+32CD (㋍): erg
U+32CE (㋎): eV
U+32CF (㋏): LTD
U+3371 (㍱): hPa
U+3372 (㍲): da
U+3373 (㍳): AU
U+3374 (㍴): bar
U+3375 (㍵): oV
U+3376 (㍶): pc
U+3377 (㍷): dm
U+337A (㍺): IU
U+3380 (㎀): pA
U+3381 (㎁): nA
U+3383 (㎃): mA
U+3384 (㎄): kA
U+3385 (㎅): KB
U+3386 (㎆): MB
U+3387 (㎇): GB
U+3388 (㎈): cal
U+3389 (㎉): kcal
U+338A (㎊): pF
U+338B (㎋): nF
U+338E (㎎): mg
U+338F (㎏): kg
U+3390 (㎐): Hz
U+3391 (㎑): kHz
U+3392 (㎒): MHz
U+3393 (㎓): GHz
U+3394 (㎔): THz
U+3396 (㎖): ml
U+3397 (㎗): dl
U+3398 (㎘): kl
U+3399 (㎙): fm
U+339A (㎚): nm
U+339C (㎜): mm
U+339D (㎝): cm
U+339E (㎞): km
U+33A9 (㎩): Pa
U+33AA (㎪): kPa
U+33AB (㎫): MPa
U+33AC (㎬): GPa
U+33AD (㎭): rad
U+33B0 (㎰): ps
U+33B1 (㎱): ns
U+33B3 (㎳): ms
U+33B4 (㎴): pV
U+33B5 (㎵): nV
U+33B7 (㎷): mV
U+33B8 (㎸): kV
U+33B9 (㎹): MV
U+33BA (㎺): pW
U+33BB (㎻): nW
U+33BD (㎽): mW
U+33BE (㎾): kW
U+33BF (㎿): MW
U+33C3 (㏃): Bq
U+33C4 (㏄): cc
U+33C5 (㏅): cd
U+33C8 (㏈): dB
U+33C9 (㏉): Gy
U+33CA (㏊): ha
U+33CB (㏋): HP
U+33CC (㏌): in
U+33CD (㏍): KK
U+33CE (㏎): KM
U+33CF (㏏): kt
U+33D0 (㏐): lm
U+33D1 (㏑): ln
U+33D2 (㏒): log
U+33D3 (㏓): lx
U+33D4 (㏔): mb
U+33D5 (㏕): mil
U+33D6 (㏖): mol
U+33D7 (㏗): PH
U+33D9 (㏙): PPM
U+33DA (㏚): PR
U+33DB (㏛): sr
U+33DC (㏜): Sv
U+33DD (㏝): Wb
U+33FF (㏿): gal
U+FB00 (ff): ff
U+FB01 (fi): fi
U+FB02 (fl): fl
U+FB03 (ffi): ffi
U+FB04 (ffl): ffl
U+FB05 (ſt): st
U+FB06 (st): st
U+1F12D (🄭): CD
U+1F12E (🄮): WZ
U+1F14A (🅊): HV
U+1F14B (🅋): MV
U+1F14C (🅌): SD
U+1F14D (🅍): SS
U+1F14E (🅎): PPV
U+1F14F (🅏): WC
U+1F16A (🅪): MC
U+1F16B (🅫): MD
U+1F190 (🆐): DJ