Create Selection
Onshape provides the Create selection dialog to make selecting related faces, such as faces that define a pocket on a model, easy. This is especially useful in certain commands, such as Delete face and Replace face. An alternative to Create selection is the Select command through the same context menu:
This command allows you to select a group of like items without having to open the Create selection dialog. You can use the collection of selected items to fill the tool dialog you open next.
For example, with one edge selected in the model below, you can select Select > Parallel edges to automatically select all the edges in parallel:
Then, when you open the Fillet tool dialog, the selection field is already populated with the selection:
To create a selection of connected edges, select an edge, then right-click to open the context menu:
From there, click Select > Loop/chain connected edges.
Alternatively, you can use the Create selection command from the same context menu to open the Create selection dialog box: