Create the rectangle with Rectangle/TL,BR, add fillet arcs at each corner with Arc/Fillet,L,L, then trim the corners with Trim/L,to,A.
XyzPilot Example
Step 1: Rectangle/P_TL=(0,60), P_BR=(100,0)
→ L0(bottom), L1(right), L2(top), L3(left)
Step 2: Create all fillets first
Arc/Fillet, L3, L0, R=10 → A0
Arc/Fillet, L0, L1, R=10 → A1
Arc/Fillet, L1, L2, R=10 → A2
Arc/Fillet, L2, L3, R=10 → A3
Step 3: Trim all corners
Trim/L0, to, A0, Start
Trim/L0, to, A1, End
[repeat for all 8 trim operations]