Room Layout Tool

Pick an item from the Library, or use Custom object to type width × depth × height plus the space you need around it.
A table entered as 150 × 75 with 10 cm behind it occupies 150 × 85 cm of floor — the tool keeps both numbers separate and draws the extra space as a hatched zone.
Drag to move. Objects snap to walls, to each other, and to each other's clearance edges.
R rotates 15°, Shift+R the other way, Shift+drag or click adds to the selection.
Ctrl+G groups what you have selected, so it moves, turns and mirrors as one piece. Double-click a member to pick it out on its own; Ctrl+Shift+G ungroups.
M mirrors left to right, Shift+M front to back — about the selection's own centre, swapping each item's left and right clearance. Duplicate first if you want to keep the original.
Labels in the toolbar (or L) hides every name tag at once. To silence just one, use the A button on its row in the list, or Name tags in its panel — a whole group at a time from the group's row.
A name tag shows the name only; sizes live in the list, the panel and the dimension lines (Dims).
Settings → Show lengths in switches the whole tool between centimetres and millimetres. Lengths are stored in centimetres either way.

Add path then click along the floor to trace a walkway; Enter finishes, Esc cancels, Backspace removes the last point.
Anything standing in a path — or in another object's clearance — is listed under Issues and outlined in the viewport.
Doors & windows are placed on a wall by distance along that wall; a door's swing is treated as space that must stay free.
A path can be one width at the start and another at the end — an aisle that opens out.

The left rail has three tabs: Add (the library, grouped and searchable, plus custom objects and pictures), Room (size, paths, doors, settings and the list of everything in it) and Parts (what the room is made of, counted).
In Parts, click a row to select every one of them, or ✎ to edit the library item behind them.
Mirroring a bench flips what stands on it — the mouse changes hands, the rack and shelf swap ends — but writing on the top is not read backwards.

Placing something from the Library links it to that library item. Edit the item with ✎ — size, clearance and colour — and everything already placed from it changes to match.
Editing a linked object does the same thing, from the other end. Unlink this one if you want to change just the one.
Custom object can save what you build as a library item, which makes it a type of its own.

Trolley — a movable table: two levels, one just above the castors and one at the height you set. Width, depth, height and colour are all it needs.
Office chair on a five-star base, and a garderobe open at the front with a hanging rail.
Object flow room — closed on three sides with a roller shutter on the fourth. Point at it and scroll to run the shutter up and down; it stops 10 cm below the top.
Select a bench and Add a wall behind it — the wall starts at bench height and stands just past the space the bench needs behind it. Select that wall to add a tool rack or a shelf to it.
The assembly travels with the bench, and dragging a rack drags the bench. Only bench walls take fittings; the room's own walls are not objects.
A rack, a shelf and a mirror take opposite ends of the wall and share its width — widen one and the other gives way. A rack is stocked like a shadow board — a row per kind, sizes running across it — and keeps its full height; a shelf is let into the wall, single or double.
Add screens or Add oscilloscope from the bench: they stand on the top, the same distance in from the back edge, sliding along and turning a little. Add keyboard and Add mouse sit at the front edge instead.
An oscilloscope can also stand on a shelf — select the shelf and add it there.
A table or trolley can carry writing on the top — laid on the surface, sized to fill it, readable from across the room.

From a picture… makes an object out of a photo. Cut-out stands the photo up at true size, front/top/all wrap it onto the box.
Floor plan underlay puts an existing plan on the floor so you can trace over it — set its scale in cm.