new viewport edit mode allowing for interaction with geometry nodes.

I propose a new geometry nodes viewport edit mode to allow for:

1. manual selection of generated geometry. Useful for:

   • A node that captures the current edit mode selection in the viewport. It's output can then be connected to the selection input of other nodes. This save time trying to figure out the indexes of elements and then specifying the ones you want with complex math nodes.

2. the display of overlayed attributes, showing any attribute present on the geometry, such as indices, normals, position, velocity, or any other user attribute. User should be able to choose which attribute/s they want to see from a dynamically populated dropdown. This information is paramount to debugging geometry node networks. Attributes could be numbers (indices, positions, etc) or visual representations of velocity as curves, or normals as lines etc.

3. manual editing of geometry at any point in the node tree. Allowing for:

   • a geometry state capture node. User could edit the generated geometry, with the starting state based on whichever node is connected to the group output or view node. For example a user might subdivide with a subdivision node, add a capture state node, click it's 'start capture' button (which changes to 'done' once clicked, then in the viewport select a few of the new faces, extrude them with the E shortcut key as you would usually in standard edit mode, and then click 'done' on the capture state node. The capture state node could be opened up like a group to reveal a node representation of the manual viewport amendments made by the user, in this case a selection node and an extrude node whose parameters are set to reflect the users viewport modifications.

     if a user modifies the nodes downstream of the capture state node, then the selection nodes would be updated with interpolated indices or kept the same at the users discretion.

     The available edit mode operators could be limited to ones that can be replicated with the available geometry nodes.