Nicholas Knutsen 

Go to File -> Options -> Editor -> AutoCorrect and check the settings for your target language.

Thanks for your reply. I have nothing checked under Autocorrect. There is nothing there that would make these replacements anyway.

Sorry I wasn't more accurate. My version: Trados Studio 2022 SR2 - 17.2.11.19134

I'm on Windows 11 23H2.

Nicholas Knutsen 

Is the target language list set to your target language and still empty?

The AutoCorrect feature from Trados Studio is the one I pointed the finger as well.

If it’s not AutoCorrect, what’s the original file format? Maybe a PDF created with InDesign? InDesign has a setting to create ligatures automatically?

Yes, it's set to my target language. But there are no "fi" or "ti" or any other kind of ligature replacements in "AutoCorrect" anyway.

The original file is an Excel file. The font is Calibri. There are no ligatures in the Excel file, but when I open it in Studio, they have been inserted. And if I type in Studio, they are automatically insterted. If I type in the Excel file, nothing happens.

Nicholas Knutsen 

Could you please insert a really small sample of the Excel file? Just one cell will suffice (as long as you confirm that sample file has the issue.

Let us know the word you are trying to write in Trados Studio and the target language. I’ll try to repro the issue.

I guess you don’t have AutoHotkey or a similar program modifying keys, right?

Nicholas Knutsen 

Do you show formatting? If so, go to File -> Options -> Editor and switch to "Show all tags, but no formatting". Maybe this can help.

www.madforest.com/test.xlsx

This word, "til", has three letters in the excel file. But in Studio, "ti" will be replaced with a ligature.

Wow, that did help! Now there are no ligatures in the source view nor when I type! I would never have guessed that, thanks!

I was a bit quick yesterday. Choosing "Show all tags, but no formatting" made the ligatures go away, but of course all other formatting is also not shown. This is unfortunate, because then I can't even see which segments are headers, among other things. This is even worse than having the ligature problem. So I'm going to have to keep the ligatures unfortunately. (It makes no difference in the finished translation, it's just an editing problem.)

In the previous version of Studio that I used, 2019, this was not a problem. I had formatting enabled but never had this ligature problem with Calibri or other fonts.

But I assume this is just an added stupid feature of Studio that can't be independently disabled.

Nicholas Knutsen 

Well. this is just a question of habit. You can see headings, list items and other structure information in the most right column of the Editor part in Trados Studio. This information is always there.
As for viewing the formatting in a software like Trados, I consider this being a nuisance. When you show formatting and the document uses a font not present on your system, Trados Studio will replace this font on the source side with something similar. As long you use ASCII, the target side may get the same font. When you go to languages using enhanced encoding like Polish for example, the substituted font may get substituted again, creating problems in the target file. Not showing formatting means, that Studio uses default font for viewing with no substitutions. Another part of this story are formatting tags, which are not visible in formatted view. Many people will then tend to use "Bold" from the toolbar in TS. But this is usually NOT the same as the tags in source. Especially when working with InDesign or similar files the layouter will literally swear, when getting such translation with hundreds of formatting errors... This is why I never view formatting in Studio. I have switched that off in the version 2011 at the latest.