I have GOOD news and BAD news, and then, GOOD news again.
Good news is: In STO there are key bindings, in the Key bind Tab, for Follow and Assist. Lax explained how to set these up in this thread.
Bad news is: This wont work in space. Reason is, there are no key binds for follow or assist listed in the space key bindings tab in game. They don't exist. They do for ground though.
Good news is: You can make them exist (sort of).
STO has a very vast open command system available in game. To see all the commands while in game, type /cmdlist in chat and press enter. Also you can see what commands STO uses for the various key bindings in the key binding tab, by just hovering your mouse over them. A tool tip appears with the key binds name and the command that STO uses. Here they are online
http://sto.gamepedia.com/List_of_console_commandsAs Lax stated. STO has an ASSIST but is not titled ASSIST in the Ground section of the Key Binds tab. It's Titled "CREW ATTACK MY TARGET"
And the command for it is "/PetCommands_Set AllToOwnerAttackTarget" With out the Quotation marks
In STO there is a key binding file for each character created. This file is in the STO folder on your computer. You can create a key bind in STO using the "/bind" command this command can do much more than that. See this guide here
http://sto.gamepedia.com/Guide:_KeybindsHere's what you need to do to get FOLLOW and ASSIST working while in Space. You will be using the "/bind' and "/follow" commands to bind FOLLOW in space to a key. You must be in Space to set up a key bind for Space. Same for Ground, you must be on the ground to set up a key bind for Ground. So Beam up to Space, so that you are in your ship. The syntax you will use is "/bind <key> <command>" without the quotes. So to set lets say F12 to FOLLOW. You will type in chat "/bind F12 Follow" and press enter. To set up ASSIST in Space to lets say F11. You will type in chat "/bind F11 PetCommands_SetAllToOwnerAttackTarget" and press enter.
While in Space, F12 will now be FOLLOW, and F11 will now be ASSIST. You will not see these key binds listed in the Key Binds Tab in game but they will exist in your characters Key Bind file in the STO directory. These bindings will persist through log out for that character until you over write them. You will need to do this for each character in your team.
Oh, by the way, if you are planning on using any of the F keys F1-F12 for a key bind in the "/bind syntax, simply pressing the F whatever key wont work in STO. While using the "/bind command you have to spell out the F key your using. So for lets say you want to use F10, you will have to type the letter F then type 1 then type 0.
Enjoy