Import and export

Command	Reads	Writes	Notes
:csv save/load	CSV	CSV	Plain text, fast
:xlsx save/load	.xlsx formulas + values	EXCEL mode: formulas + cached values; other modes: values only	:xlsx load switches to EXCEL
:pd save/load	CSV/TSV/Excel/JSON/Parquet	same	Uses pandas; row 1 as headers

:xlsx load translates Excel formulas into gridcalc's EXCEL grammar and reads every sheet.

INDIRECT and 3D ranges (Sheet1:Sheet3!A1:B2) are deliberately unsupported, because they would defeat the static dependency graph. Functions outside the auto-loaded library produce #NAME?. The full list of what does not cross the boundary is in Limitations.

The xlsx path goes through a C++ extension wrapping OpenXLSX rather than a pure-Python reader, which is why the core install needs no third-party runtime dependency to read a spreadsheet.