Consider llama.qtcreator suggestion in Qt Creator 17.0.2:

qt-creator-17.0.2-tab-and-shift-tab.mp4

The Tab suggestion works as expected.

• suggestion is displayed correctly
• insertion with Tab will insert the whole suggestion
• cursor is moved after the suggestion

Shift-Tab works inserting one line after another.

Qt Creator 18.0.0 has a different behavior:

qt-creator-18.0.0-tab-and-shift-tab.mp4

The Tab suggestion has a different behavior:

• suggestion itself has one empty line below
• insertion with Tab will preserve the empty line, and the cursor doesn't move

The Shfit-Tab suggestion is:

• initially displayed with a new line
• after the Shift-Tab, the line is inserted at the desired position, and visually it moves one line up

As a user I would expect the behavior not to change.

It might be that Qt Creator 18 has fixed some issue in Qt Creator 17. The suggestion insertion in llama.qtcreator is done at https://github.com/cristianadam/llama.qtcreator/blob/main/llamaplugin.cpp#L821