Explore edit by selection functionality

**Description**

PR #108 introduces editing memory values by group. However, to give the user more flexibility in editing values, we could explore an additional edit by selection. This would allow users to more selectively change a sub-selection within a group or a selection that spans multiple groups/parts of subsequent groups without being bound to the MAUs per Group setting. A first draft was created by @colin-grant-work for discussion. See #110 .

Topics to discuss to drive this further
* Use cases and feasibility of selecting parts within a group and across multiple groups.
* How should the selection be interpreted and translate into the edit box.

**Additional information**