Installed TextBlaze on my Win 10 system a few days ago. It does not auto-start when computer reboots. Under Apps/Programs, TextBlaze is set to auto-start. Only way I was able to get it to run at start-up was to manually create a shortcut of the app and copy it to the Windows start-up folder.
There is no setting inside of TextBlaze app itself to tell it to start at startup.
We have fixed the auto start issue in the MS Store app build in the latest version (v1.4.2) so if you want to force update the app to the latest please uninstall and install it again from here.