No Option to Pin App

Hi. For Zorin OS Lite, if I right-click some apps, I can't pin them. (See pic). How can I pin it?

You can select "Make Custom Launcher" to create a launcher for the panel.
Once created, you can right click the Panel, use the arrow right to move to the popover menu for Panel Settings.
In your Panel Settings PopUp window, click the Items tab. In this tab, you can edit all aspects of the launchers, their positioning on the panel etc.

When making a custom launcher, what do I put under "Command"?

Please try this as the command:
blender %f

Thanks. It works now, except that pressing Super+3 doesn't open the Blender app (it switches to Blender if it's already open, though). I wonder if this is because I have more than one version of Blender on my computer?

Maybe. Which versions do you have?
You might go to Settings > Keyboard > Application Shortcuts tab and check your Blender keyboard shortcut. See if it matches the command used for the launcher.
Click the Blender Shortcut in the list, then click the edit button on the bottom toolbar.

I just downloaded the latest official release of Blender 2.93. I also have a bunch of 2.93 beta versions, as well as 2.79b. I might switch over to 2.93 now that it's officially released and has lineart.