Merge button greyed out

This is my first post, so please bear with me if I make a mistake.
I am using Libreoffice Calc and am amending a previous spreadsheet. I need to split cells, but the 'merge/split cells button is greyed out. I have tried looking online and followed a few tips, but it didn’t work. I tried going to Edit, Changes and de-selected Record, that didn’t make any difference. I have merged cells in previous versions of this same spreadsheet, but I can’t seem to do it this time. I know you can have the split horizontal or vertical, but I can’t seem to find the answer. I would be grateful if anyone could give me some advice.
Thank you.
p.s. I can’t seem to post with a tag, but I don’t know what that is, so I’ve just put any word in.

@Lupp answer it’s really clear. If what you want it’s split cell content avoiding formulas, you can try Menu/Data/Text to column.

Things are unclear to me. Split (horizontal or vertical) of single cells or for the cells of a range is possible in text tables (Writer) but not in spreadsheets. In Calc you will get a ‘Split’ option only for a cell covering the area of two or more actual cells that were “merged” in advance. (A true merge will never be done. the "merged cell will logically be identified and addressed as the topmost leftmost cell of the merged range. The cells seemingly vanished will still exist, may be referenced, and can have content.) The ‘Merge’ option will only be offered if a mergeable range is selected.

Best you would attach (or somewhere upload) an example ods demonstrating your problem.

(Editing with regard to the below post)

It actually seems to me you had a table in a Writer document once. Otherwise i cannot consistently interpret your post,

If you Copy/Paste a rectangular range from a Calc spreadsheet into a Writer document you will get an “OLE” version of the spreadsheet but not a text table like one created in writer. The only workaround I know, is to ‘Paste Special…’ the contents of the selected range as ‘Unformatted text’ and subsequently convert it into a table with the help of ‘Table’ > ‘Convert’ > ‘Text to table’.

On the other hand it is not clear to me for what reason cells should be split. Simply leaving empty not needed adjacent cells might also match your needs.

Hello Lupp

I apologise for being so vague that you don’t understand my query, but I am also grateful that you attempted to help me anyway.

I have a spreadsheet that I constructed to enable me to take lots of supplements, I unfortunately have osteoporosis and have just this week fractured my third vertebrae in under a year!!! I have so many different things to take that I made the spreadsheet to help me to remember everything. Some things I have to take up to three or four times a day, so I split the cell into two or three vertically and was able to tick the relevant part cell. I then changed the list and did away with the split cells and just listed everything individually. Now I need to go back to the version of the list with the split cells, the merge/split cells in Calc is greyed out.

Do you think that I’m mistaken and that I actually split the cells in Writer? With this thought in mind, I have just copied and pasted the table from Calc into Writer, in order to try to do it that way. However, I cannot edit the page, it acts like it’s a photo or graphic and won’t let me click onto the table.

I understand this is another problem altogether, but if you can understand my predicament from this description and can in any way help, I would be very grateful.

Thank you for taking the time to help.