Hi @Mugurian,HL,Helen,THE R ,
Thank you for posting in this community.
There is no out-of-box solution for doing so as mentioned by (Sukie Qi MSFT) on https://answers.microsoft.com/en-us/msoffice/forum/all/remove-table-borders-from-table-in-sharepoint/16c76e84-5c71-4b89-afbe-d8acf64cea26
However, per our search, it seems code may help change theme of table. Use theme colors in your SharePoint Framework customizations | Microsoft Docs
You could implement a solution where:
1: You choose tables who borders should be transparent as the option "Theme-colored plain"
2: You set the CSS for "Theme-colored plain" to border-color transparent, which will only affect tables that have this style:
table.simpleTableStyleTheme {
/* ... */
border-color: "transparent!important;";
/* ... */
}
Hope the information can help you.
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