LaTeX.org

Comparing the two proposed solutions:
a) replace the original TeX.xml file at each TXC installation
b) creating a new file (for example My_Tex.xml) with my own commands
I liked the second best and tried it.

However, one should notice that the commands cannot have the same name as in TeX.xml. For ...

How to easily change the language adopted for spelling purposes? (without restarting and changing the personal directory)

If I go Project => Properties => Project language, this will not (of course?) change the language used by the speller checker.

I need to go Tools => Options => Spelling ...