In QCAD Pro, I found that setting the application preference to disable "Text above dimension line" does not transfer to new drawings.

My setup:
QCAD Professional version: 3.28.1.0
Date: Mar 30 2023
Qt version: 5.8.0
Compiler version: gcc 4.8.1
Build date: Mar 30 2023
Revision: ca7ec144abd203d2a68ca91c0ff0684868ba08a5

OS: Xubuntu 23.04
Kernel: 6.2.0-25-generic
Resolution: 1920x1200
DE: Xfce 4.18
WM: Xfwm4

Demonstration procedure follows:

Fresh install QCAD Pro (no previous config file);

Edit --> Application Preferences

Under "Defaults for New Drawings", select "Dimension Settings"

Under "Dimension Style", "Text above dimension line" is enabled by default. Uncheck it, then press Apply button.

Change one or more other settings; for instance "Linear Dimensions" to Decimal, or the Precision. Press Apply button accordingly.

Press OK button to dismiss Application Preferences.

Quit out of QCAD Pro.

Reopen QCAD Pro. Create something that can be dimensioned, and dimension it. Label will appear above the dimension line.

Edit --> Drawing Preferences

Under "Dimension Style", "Text above dimension line" is checked, contrary to the Application Preference setting. The other preference settings are in effect.