DraftSight Dimension height  is controlled by Textstyle.

In order to change it please follow below steps:

1. Launch DraftSight.
2. Open the drawing file in which you are unable to edit the dimension text height.
3. In the command line, type TEXTSTYLE and press Enter.
4. The Text Style dialog box will open.
5. In the Height field, change the value from 1 (or any non-zero value) to 0, then click Apply and OK.
   (Setting the height to 0 allows the text height to be controlled individually.)
6. Select the dimension text you want to modify.
7. Right-click and choose Properties.
8. The Properties panel will open. If needed, right-click inside the panel and enable Display Icons with Labels.
9. Under the Text section, locate Text Height and adjust it according to your requirement.

After completing these steps, you should be able to edit the dimension text height without any issues.

Posted on behalf of @PD