Here are a couple helpful hints I picked up in training, enjoy!
When you want to see just a few objects in 3D and modify/add/delete from them:
Select the objects you want to see.
Select "isolate objects"
Choose either edit in section, plan, or elevation.
Follow the command line prompts to cut the section or elevation.
Now your objects will pop-up in a separate window.
You can add objects (pipe, duct, equipment, aec content) or modify objects as desired here.
Once you are done, click on the "edit in view" pop-up toolbar button to exit this window.
Command line commands:
You can type in the first letter or two and then hit tab and it will tab you through all of the commands that are available with those letters.
Keep in mind the duct and pipe commands are actually "add duct" and "add pipe" so it will not be under "d" for duct or "p" for pipe, it will be under "a" for add.
If you want to see all the available commands used in ABS: at the command line type "arx" then choose "c" for commands.
Content Browser: If you want to keep this window on top all the time:
Open the content browser.
Right click on the top of its title bar and choose "Always on top".