Copy below content, Remove unwanted action from that and put the file content in extension module(web-extension/site-data/extensions/*-extension-module.xml).
<?xml version="1.0" encoding="UTF-8"?>
<module>
<idRemove default Multi actions</id>
<version>${project.version}</version>
<auto-deploy>true</auto-deploy>
<auto-deploy-index>101</auto-deploy-index>
<configurations>
<config evaluator="string-compare" condition="DocumentLibrary" replace="true">
<multi-select>
<action type="action-link" id="onActionDownload" icon="document-download" label="menu.selected-items.download" />
<action type="action-link" id="onActionCopyTo" icon="document-copy-to" label="menu.selected-items.copy" />
<action type="action-link" id="onActionMoveTo" icon="document-move-to" permission="Delete" label="menu.selected-items.move"/>
<action type="action-link" id="onActionAssignWorkflow" asset="document" icon="document-assign-workflow" label="menu.selected-items.assign-workflow"/>
<action type="action-link" id="onActionDelete" icon="document-delete" permission="Delete" label="menu.selected-items.delete" notAspect="hwf:hybridWorkflow,sys:undeletable" />
<action type="action-link" id="onActionCloudSync" asset="document" icon="document-cloud-sync" permission="CreateChildren" label="menu.selected-items.cloudSync" notAspect="sync:syncSetMemberNode" syncMode="ON_PREMISE" />
<action type="action-link" id="onActionCloudSyncRequest" icon="document-request-sync" label="menu.selected-items.cloudRequestSync" hasAspect="sync:syncSetMemberNode" syncMode="ON_PREMISE" />
</multi-select>
</config>
</configurations>
</module>
