I'm having the same problem. I want to change from Times New Roman to another font but:
1 - Trying to make the change directly in the Normal template file doesn't work.
2 - Trying to make the change in a new document, going through the respective menu and dialog boxes to apply the change to all documents based on the Normal template doesn't work and brings me the following message:
It's Brazilian Portuguese for (freely translated):
The file C:Users\xxxxx\Documents\SoftMaker\Templates 2018\Português\Normal.tmvx cannot be opened
It happens when TextMaker is set to Brazilian Portuguese (my mother tongue and system language). But if I set the TextMaker default language to English (US), I can make that change. So the problem has to do with the Brazilian Portuguese setup.
How to fix it? TIA.