I am able to change the indentation rules via Preferences-sublime.settings or C++.sublime-setting, namely
// The number of spaces a tab is considered equal to
"tab_size": 3,
However, this does not seem to affect my .h files no matter what I do.
Is this a known bug in Sublime Text 3 or am I missing something?
Please help…
Your problem might be due to this:
// Set to false to disable detection of tabs vs. spaces on load
"detect_indentation": true,
This is turned on by default, and if you still have it on there may be something about your header files that causes Sublime to detect that the indentation is different from your settings, which overrules the setting you provided.
As such, if you have that setting turned on, turning it off may resolve your problem.