There is a video on user-defined fields here.
https://www.youtube.com/watch?v=Fa0zkvCSokE
But as everyone points out, GRID is not user-defined. If it is not showing, it could have been hidden and you need to merely unhide it. Click the padlock button so the hasp is open, and click the trash can icon that appears. Unhide fldGrid and lblGrid. Drag to where you want them on the form.
I wouldn't do a reinstall at this point. Chances are that replacing the main log form will fix it. Go to the LOGic install folder (usually c:\program files )x86)\LOGic. Then go into the logdata folder, then logforms. Delete or rename main.logform. Reinstall the latest update. This will get back the factory main log form. Download it before you delete main.logform (Click "Retain..."), or run the UPDATER command to do it outside of LOGic. The default form has the GRID field showing.
Call me at 770-307-1496 and I can log in thru Team Viewer and take a look.
Tnx & 73,
Dennis WN4AZY