How to use object's Transform Origin point while the object is not selected ?

[HrvojeL]

How to "lock" object's Transform Origin point to be available for snapping even after the object is not selected anymore ?

I have YELLOW Equilateral Triangle and I want to extend the WHITE and RED triangles to the Transform Origin point of the YELLOW triangle (please see the picture).
How can I do that ?

[GarryP]

I don’t think you can do that, but if I’m wrong I’m sure someone will correct me.
In the meantime, if you don’t have to do this a lot, you can drag/snap both a vertical guide and a horizontal guide to that point, then manipulate your other shapes according to the guides and then remove the guides.