I use UEStudio, but not the resource editor because I programing firmwares and not Windows applications. So I can't really help you. If no user of UEStudio with resource editor knowledge answers, you better ask IDM support per email. I'm sure, the support guys will help you.
It would be fine if you post here what the problem was and the solution which finally solved it.
Ask IDM support also what is wrong with your post counter. It shows -1 although it should be 8.
Just a few things which I know about Windows resources. Every resource ID symbol must be defined in the corresponding .h file (normally resource.h) where a line like
#define IDC_SLIDER1 x
must exist with x is a positive integer number.
IDC_SLIDER1 is a typical default symbol name for slider resources if a user does not specify a special symbol name. When you open grubbtestRC.rc you should see at top of the file the #include instruction for the header file with the definitions.
What happens when you open the properties of the slider and give it a meaningful ID name which is also better readable in the program code? Does UEStudio then add the necessary define into the include file?
Best regards from Austria