I'm on MacOS 10.15.7, using BBedit 13.5.5. Under "Go ->" There is only Go to Line Number. I want to go to character 145 of the file.
Here's a crib from page 103 of the user manual (you'll find it on the Help menu):
Alternatively, you can jump to an absolute character offset, by using the ‘line:column’ syntax but leaving the ‘line’ blank or specifying it as zero. For example, entering “0:1500” or “:1500” will cause BBEdit to place the insertion point before the 1500th character in the document. (The range syntax works too; so you could use “0:12-0:56” to select characters 12 through 56.)