You may use the Element-Rollup window in order to make entries in lists viadrag&drop.
Open the file Demo.gpn
Open the Element-Rollup via the Start tab.
Activate in the Element-Rollup the room tab.
Select in the Element-Rollup a room, in the example below it is the pyhsics lab. and drag the room to the teacher master data window. Drop it in the field room of teacher Gauss.
You now have allocated the physics lab. to teacher Gauss via drag&drop.
As soon as you move the Element-Rollup on your screen, symbols directing to the 4 edges of the window appear at the edges (and in the centre).
Dropping the Element-Rollup at one of the symbols fixes it to the respective edge.
Please note that you can add (or delete) further columns via the context menu of your right mouse button.