Not to my knowledge. LaunchBar is built around Abbreviations, not modifier key keyboard shortcuts.
LB uses some keyboard shortcuts, but these are for meta functions, like Shift-Cmd-I (Show in Index), Cmd-G (Get Finder selection), and so on.
An Abbreviation is a sequence of letters (or one letter) typed into the LB window, for example, TE for TextEdit, or GO or G for Google search. As LB learns from your habits, these abbreviations are dynamic, i.e. you establish them simply by using them (although you can also manually assign an Abbreviation). Check out the corresponding section of the LaunchBar Help.
So, LB’s way to get to a Google search would be this:
- In LB’s settings, make sure you have set up a modifer tap to invoke LB (for example single tap Command key). This is faster and more convenient than to use a combo shortcut like Cmd-Space or similar, especially if you use LB a lot.
- Train LB to recognize G as your Google Abbreviation (or assign G manually).
Now, all you have to do to invoke a Google search is: Tap the Command key > Type G > Press Spacebar.
This is one more keypress than the shortest possible modifier key keyboard shortcut (e.g. Cmd-R), but the advantage is that you don’t have to remember any key combo (except that G means Google) and that you don’t steal modifier key combos from other apps or the system.
If you prefer “traditional” modifier key shortcuts, I would recommend to try other apps, like KM, or Alfred, or Apple’s Shortcuts app, Services, etc.
Edit:
Instead of pressing the Spacebar, you can also just hold the last Abbreviation key. With this, you are down to exactly two keypresses: Tap Cmd > Type and hold G.
See Instant Open.