Hello Librecaduser,
I will try to help you create a block.
The problem here will be that I use a later version of LC: Version: 2.1.0-alpha
Commit: db581f4
Compiler: GNU GCC 4.9.1
Compiled on: Apr 1 2016
Qt Version: 5.4.1
Boost Version: 1.53.0
But lets try:
First it does not matter if you are in isometric or not, LC is just a 2D CAD program.
Once you have selected all the entities you need to join, select the tool "Create a Block", it looks like a rectangle with a circle in the lower left corner and a green point in the lower right. Specify a reference point (you will need it if you copy it somewhere else).
Once you click on the point chosen a small window will open: "Block Settings", it will ask you for a Block Name, give it a name and OK it. Your block is created, now all the entities you selected are just one unit.
If you want to save this block for future use you need to make sure you save it in the block list. I suggest that you read the following document for more on that:
http://wiki.librecad.org/index.php/Blocks.
I am working at the moment on an instruction document for all the drawing tools, it is not complete yet but I join here a PDF version of what exists:
Tools_instructions.pdfLast but not least, if you want to break your block back into the various original entities, select your block and click on the Explode tool in Modify.
I hope it helps,
Regards,
Christian