Thanks for trying it, and the spreadsheet repo is great prior art — I'll dig through it.

Drag-fill. Not yet, but the parts are mostly there. The formula layer already carries abs_col/abs_row through tokenization → AST → eval, so $A2 + B$1 parses correctly today; what's missing is the editing op that copies a formula across a range and shifts only the relative components. Opened #17 for it. The tricky part isn't the rewrite, it's the keybinding — Vim doesn't have an obvious idiom for "drag," so I'm leaning toward a visual-selection + fill-from-anchor key (Y is a candidate) or a :fill command. Open to suggestions if you have a feel for what works in a modal editor. It also needs to land on top of the bulk-undo work in #8/#9 so a fill is one undo step instead of N.

bar() / inline visualizations. Love it, opened #18. The interesting design call is whether BAR returns a CellValue::Visual { … } that the renderer dispatches on (correct under column resizes, but ripples into CSV export, copy/paste, and how SUM treats a visual cell), or whether it just returns a string of block-drawing chars at eval time (trivial to add, but width gets baked in at compute time which is wrong). The first is the right answer; the second is a tempting MVP. SPARKLINE(range) is the natural follow-up once the abstraction settles.

#17 — https://github.com/garritfra/cell/issues/17 #18 — https://github.com/garritfra/cell/issues/18