Table - Split Table is greyed out when you are in a cell that falls across a page boundary and your cursor is in the part of the cell showing on the over-the-page part of the cell, but Split Table is not greyed out when you are in the prior bottom-of-the-page part of the cell. This is shown in the attached item.
Steps to Reproduce:
User Profile Reset: No
Created attachment 149868 [details]
Created attachment 149869 [details]
Sample Document that exhibits it
Actually I think it's worse/more general than that - I'm on a cell that's at the top of a page and can't split the table there as the cell above it falls on the previous page, but if I add some paragraph marks prior to that above cell to shift them both down so they are on the same page the Split Table becomes available.
I confirm it with
Version: 184.108.40.206.alpha0+ (x64)
Build ID: 91cdf22b88a4f7bec243c8fb187627e766d3294c
CPU threads: 4; OS: Windows 10.0; UI render: default; VCL: win;
TinderBox: Win-x86_64@42, Branch:master, Time: 2019-03-08_00:38:10
Locale: en-US (de_DE); UI-Language: en-US
Version: 220.127.116.11 (x64)
CPU-Threads: 4; BS: Windows 6.19; UI-Render: GL;
Gebietsschema: de-DE (de_DE); Calc: CL