Why can't symbols be copied between library parts

Assuming you are in the schematic library editor and have the SCH Library window showing (View > Library).

Method 1: Right click on existing symbol, Copy. Left click in window, Paste. A copy of the symbol is created.

Method 2: Open an existing symbol in the editor window. Select an element (line, arc, pin), click Copy (Ctrl+C) and left click. Use the library window to open a different symbol, use Paste (Ctrl+V) to copy the element into that symbol.

I think the complaint maybe about simply not being able to draw a box around the elements (primitives) of the symbol in the SCH Library and then copy/paste them to another symbol.  If I try this with a very simple symbol such a test point that has one pin and a graphic line and a circle then it appears to correctly select the primitives and the option to copy them comes up in the right-click options.  However, if I then make a new symbol and try to paste the pin and primitives into the symbol it acts as if I copied the part (it makes TESTPOINT_1) instead of pasting the primitives to the new blank part.  Similarly, if you try CTRL-A and then CTRL-C and then pick the blank part and paste you will instead make TESTPOINT_2,.

After doing this a few times, my software got confused and it appeared that I was not able to pick and copy individual primitives.

I was able to get this to work by selecting individual primitives with SHIFT-LEFT-CLICK to pick several and then copy/paste to the new symbol.

I have been making some of my symbols this way; I use a template symbol such as IC-Template, RES-Template and copy/paste to a new symbol (IC-Template_1).  This copy then has all the default parameter names and default values that I wanted from my template.  Then I alter the primitives as I need them.  This might include possibly copy/paste from some other symbol or perhaps from something I pulled in from the vault.

Another feature you need to know is that the paste order can make primitives hide other primitives, such as having a filled box obscure the pins.  To fix that you must select the primitive and then use the Tools> Move > Send to Back command.

So my conclusion is that it does work but is a bit dodgy.

There does seem to be some unreliability with the copy command. The drag a rectangle to select does sometimes work with Ctrl+C but other times seems to fail, deselecting and then reselecting will often allow the copy to take place. I will report this to Altium for investigation.

Also, it looks like after making the selection and then choosing copy you need to pick another point as origin of the copy with an additional left click; at least it works more consistently for me with this.  Sometimes this takes and sometimes it doesn't.  Then if you right click, the paste option will be either grayed out (it didn't take) or will be normal.

It is still unreliable but perhaps Simon can at least try it again knowing you need to make the extra mouse click to set the origin.  To add to the confusion, the cut operation will delete the selection but you cannot always paste it back.

Also, it looks like after making the selection and then choosing copy you need to pick another point as origin of the copy with an additional left click; at least it works more consistently for me with this.  Sometimes this takes and sometimes it doesn't.  Then if you right click, the paste option will be either grayed out (it didn't take) or will be normal.

It is still unreliable but perhaps Simon can at least try it again knowing you need to make the extra mouse click to set the origin.  To add to the confusion, the cut operation will delete the selection but you cannot always paste it back.