MathML3 provides a "columnspan" attribute for the <mtd> element and this is implemented in WebKit. MathML Core aligns to the HTML name, which is "colspan": https://w3c.github.io/mathml-core/#entry-in-table-or-matrix-mtd Chromium bug (with tests): https://chromium-review.googlesource.com/c/chromium/src/+/4061476 Firefox bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1814346 This bug is about supporting "colspan" (and disabling "columspan" when MathMLCore is enabled). That should be relatively easy to do: https://searchfox.org/wubkat/search?q=columnspan&path=&case=true®exp=false
<rdar://problem/104935841>
Closing per https://github.com/w3c/mathml-core/issues/180#issuecomment-1484532747