guess it has to do withthe new scintilla control but not sure, because it happened after i played with a powerbasic-sample (scintilla-control-splitter). One or two days later i discovered thinair will not show any code.
several tries to re-install failed, sinc a few days no more scintilla-codewindow, the splitter splits but stays invisible

...Scintilla 5 has moved the lexers from Scintilla into a new Lexilla project....
https://www.scintilla.org/ScintillaDoc.html

for the meantime i user Everedit (still testing how to configure but i am certain EVEREDIT can be scripted using thinBasic without any problems. Try CTRL+ESC (command-input) - you can have multiple stdOut-windows at once,

Screenshot upload does not work

Currently englsh only and some far east asian languages- but its surprisingly good - one of the best - because easy to use and full of features (i have it already running thinbasic-scripts, showing the buggy line (if any) and opening included files when clicking on the name - but not syntax highlight yet. Guess its C# or vbscript to make lexer (.MAC-files)
CTRL+M opens file-browser, CTRL+O the list of open files (tabs are wasting space...), CTRL+U opens the treeview that shall display the code-overview in future,
Its pretty lightweight, portable, and fast. it's worth a try and - regarding the developement speed of thinair (syntax-tree shows wrong items, file browser shows no tBasicI-files and always resets to "dont show any items that are not loaded already")- search & replace works only one by one replacement and is not able to apply any regex, no macros for script-developement its probably much faster to configure some ready to use-coding-editor like this.