Chart rendering in Excel 365 has become extremely slow in specific excel spreadsheet

Changed this to a subanswer, as this is probably is not so related to why. it is rather an explenation to why I changed the background colours:

It is because some of the charts had turned transparent (not specified/triggered by me, but rather "a unwanted trigger" by the macro code (written by me).

I have checked the macro code thouroughly with F8:

Only one chart is supposed to transparent in the sheet, as I make png/gifs out of a chartobject with a few charts embedded (as it is not possible to draw png-s from a selection of charts).

However, that code alters a few "completely other" charts as well simultanously (which are not selected/activated by me (have chekced with F8)) => Seem to be rather that several charts is given the same ID (names are always different, so rather something else, like ChrtObj-Number or something similar), even though I only choose one specific.

This has also happened to me earlier in excel-vbe where two properties or objects may be activated and altered simultanously,

e.g. A) "line style" of both 1) chartserie lines and 2) -markerlines can be changed simultanously, or

B) two series are given the same format even though only one is chosen... (E.g. as discussed here: https://answers.microsoft.com/en-us/msoffice/forum/all/changing-color-for-one-data-series-changes-color/56add894-36b6-40b6-9c99-300df914a0c9 => The fix is to start all over again, and don't use copied charts in that case...)
C) etc.

Hello Hallvard

I’m Adeyemi and I’d be happy to help you with your question.

There could be several reasons why chart rendering in Excel 365 has become slow. Some users have reported that chart rendering has slowed down after an update. You could try launching Excel in safe mode and see if the issue persists. If it doesn't, you can try disabling add-ins to see if that resolves the issue. Reference: https://answers.microsoft.com/en-us/msoffice/forum/all/chart-rendering-in-excel-365-has-dramatically/b687b78f-f81e-4004-a425-72b3320c4df5.

Another user reported that charting became slow when the chart styles option was enabled in the chart formatting ribbon. They found that collapsing the ribbon improved performance.

If you feel that this should be classified as an issue, you can report it to Microsoft through Excel's feedback option here: https://support.microsoft.com/en-gb/office/how-do-i-give-feedback-on-microsoft-365-2b102d44-b43f-4dd2-9ff4-23cf144cfb11#platform=Windows

I hope this information helps!

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Regards, Adeyemi

I found the reason, I was adding series by selecting cells and then select by .xldown,

so a few series (by mistake) included several millions of cells and this slowed down everything exceptionally.

Sorry for the inconvenience, and thank you for the help anyway!