This is all based on a beginners view of FreeCad, one with little experience in any CAD program. Something is an issue if it has given me a problem. This may be just because I do not understand the program or am approaching the problems the wrong way. In other case I may have come across things that bother other users and the solutions may be of some help. In other cases the issue may be a bug or limitation of the program.
These are issues that I think I have solved. The solution may not work for you, there are so many things that can go wrong.
I Cannot Rename the top of the Component Tree
Solution: This is the file name, use the File -> Save or File -> Save As menu
Pasted Object but "Nothing" Happened
Solution: You may be really zoomed in. Use the view all icon. Always use this when you do not see what you expect. Also look for tiny objects that you may miss. Look in the tree to see if component is there, turn off the visibility of other components. Your new component may also be inside an existing one.
Icon Disabled, Why?
This happend when I wanted to use the binary operation in the Part ... workbench. It may happen for other similar icons. Solution: The icon had already been pressed and opened a dialog that was in the background and not visible. Forget how I found and closed it, but look around your gui, perhaps will show in the Windows menu choice?
Could Not Fuse More than 2 Objects
Solution: I was confused over 2 icons that are almost the same, one is for boolean operations which looks a lot like the fuse one!
Keeping Track of Dimensions Can Be Confusing
These are issues for which I have not found much of a solution.
Have not found a way to name the elements in the sketcher workbench. Google says.....
Selecting Elements in Sketcher
Without the ability to name elements it is hard sometimes to select the element you want ( normally if elements lie on top of each other ) Howerver, if you put the cursor over the element list the particular element in the sketcher view changes its color so you can tell which one it is. You can also change the element type in the upper right hand corner. Mess with it and it may help.
Copy Paste in Sketcher
Need more research here.