Hi @Ankit_smart,
i think it is possible with the Continental Nodes
https://www.knime.com/community/continental-nodes-for-knime-xls-formatter
There you have layouting and formatting options (however never used them myself - so cannot help in detail)
Another solution to keep the formatting is using the POI Library in combination with a java snippet, however you would need to a bit of code for that:
https://poi.apache.org/
We use the POI Library to just write to a template excel instead of overwriting the sheet.
So you can copy a knime table to an existing excel file and change the formatting there
(would be nice if they could add that feature to the excel writer)