How do I define a value for a dimension as a function of a sibling dimension value?
E.g. I may want to define Founder A’s ownership % as a function of the Employee Option Pool and the Seed Investor’s.
Hey Simon 
You’re definitely on the right-track! In the Founder A input field, after you type “Shareholders”, you’ll want to hit the time button (where it says “all” in your screenshot), and click “Custom”, and then type “t”. “t” basically means the current timestep - in this situation it looks like your inputs don’t vary over time anyway, so “all” would work out the same. Then by hitting the category icon you can filter for particular category items.
For example, if you wanted to have Founder A & Founder B’s shareholding be an equal split of whatever remains after Pre-Seed Investors and the Employee Option Pool, the formula would look as follows.
