According to tracemalloc, the top 10 differences after opening and closing 7azs once are:
Top 10 differences:
/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/chimerax/atomic/molc.py:80: size=3504 KiB (+3504 KiB), count=53655 (+53655), average=67 B
/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/chimerax/atomic/molarray.py:159: size=2525 KiB (+2525 KiB), count=11 (+11), average=230 KiB
<frozen importlib._bootstrap>:228: size=549 KiB (+549 KiB), count=6520 (+6520), average=86 B
/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/chimerax/atomic/molarray.py:86: size=261 KiB (+261 KiB), count=21 (+21), average=12.5 KiB
/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/chimerax/atomic/molarray.py:1393: size=40.4 KiB (+40.4 KiB), count=171 (+171), average=242 B
/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/ctypes/__init__.py:510: size=24.4 KiB (+24.4 KiB), count=393 (+393), average=63 B
/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/chimerax/core/orderedset.py:36: size=20.4 KiB (+20.4 KiB), count=134 (+134), average=156 B
/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/numpy/core/_internal.py:255: size=19.8 KiB (+19.8 KiB), count=169 (+169), average=120 B
/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/chimerax/graphics/drawing.py:255: size=14.2 KiB (+14.2 KiB), count=26 (+26), average=558 B
/Users/chimera/Applications/ChimeraX_Daily.app/Contents/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/chimerax/atomic/molobject.py:1461: size=10.1 KiB (+10.1 KiB), count=9 (+9), average=1146 B