Nodes. Use Node Tool to manipulate.

Ellipse Tool.

Use Trace Bitmap dialog.

Use Interpolate effect.

Use Pattern Along Path effect or Create Tiled Clones dialog.

Dropper Tool.

Use Middle Mouse Drag with any tool.

Draw a “Cutting” path, then use Path → Cut Path (Ctrl+Alt+/) or Path → Division (Ctrl+/). See Path Operations.

Use rubber-band selection.

Use Measure Path effect.

Calligraphy Tool.

Paint Bucket Tool (coming in v0.46).

Dialogs.

Star Tool.

Draw a Rectangle, then use the Grid Effect.

Use Select Tool (see Transformations), or from the keyboard, use h and v.

Use Node Tool; see node sculpting.

Use Select Tool (double click on object to get rotation handles: see Transformations), or from the keyboard, use [ and ].

Use Select Tool (see Transformations), or from the keyboard, use > and <.

Draw a “Cutting” path, then use Path → Cut Path (Ctrl+Alt+/) See Path Operations. If you just want to open a path in one place, create a new node (double click on path with Node Tool) and then click on the icon.

Use Select Tool (double click on object to get skew handles: see Transformations).

Use Path → Simplify (Ctrl+L) command.

Text Tool.

Zoom Tool. You don't need to hold Ctrl down when using + and − keys.