Create a custom page.
add table displayer from reporting.Enable csv and excel export under Display tab.Then click ok.
click on 'Export to Excel' feature available on right corner.

Then check the server.
Getting below error:

'14:16:51,879 ERROR [org.kie.workbench.common.services.refactoring.backend.server.indexing.AbstractFileIndexer] (Thread-251) Unable to index 'default://master@dashbuilder/datasets/tmp/9b79003c-5c1a-426d-bf3b-c56c4cd76441.xlsx'.: org.drools.template.parser.DecisionTableParseException: No RuleTable cells in spreadsheet.
at org.drools.decisiontable.parser.DefaultRuleSheetListener.getRuleSet(DefaultRuleSheetListener.java:151)
at org.drools.decisiontable.SpreadsheetCompiler.listenerToString(SpreadsheetCompiler.java:125)
at org.drools.decisiontable.SpreadsheetCompiler.compile(SpreadsheetCompiler.java:121)
at org.drools.decisiontable.SpreadsheetCompiler.compile(SpreadsheetCompiler.java:93)
at org.drools.decisiontable.DecisionTableProviderImpl.compileResource(DecisionTableProviderImpl.java:74)
at org.drools.decisiontable.DecisionTableProviderImpl.loadFromResource(DecisionTableProviderImpl.java:42)
at org.drools.compiler.compiler.DecisionTableFactory.loadFromResource(DecisionTableFactory.java:36)
at org.drools.compiler.compiler.DecisionTableFactory.loadFromInputStream(DecisionTableFactory.java:32)
at org.drools.workbench.screens.dtablexls.backend.server.indexing.DecisionTableXLSXFileIndexer.fillIndexBuilder(DecisionTableXLSXFileIndexer.java:56)
at org.kie.workbench.common.services.refactoring.backend.server.indexing.AbstractFileIndexer.toKObject(AbstractFileIndexer.java:78)
at org.drools.workbench.screens.dtablexls.backend.server.indexing.DecisionTableXLSXFileIndexer$Proxy$_$$_WeldClientProxy.toKObject(Unknown Source)
at org.uberfire.ext.metadata.io.IndexerDispatcher$IndexerJob.processNew(IndexerDispatcher.java:255)
at org.uberfire.ext.metadata.io.IndexableIOEvent$NewFileEvent.apply(IndexableIOEvent.java:62)
at org.uberfire.ext.metadata.io.IndexerDispatcher$IndexerJob.processEvent(IndexerDispatcher.java:235)
at org.uberfire.ext.metadata.io.IndexerDispatcher$IndexerJob.processEvents(IndexerDispatcher.java:211)
at org.uberfire.ext.metadata.io.IndexerDispatcher$IndexerJob.get(IndexerDispatcher.java:188)
at org.uberfire.ext.metadata.io.IndexerDispatcher$IndexerJob.get(IndexerDispatcher.java:159)
at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1604)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
'
Before 7.6.0 server is throwing another error on same functionality.see the error below
'
15:06:31,682 ERROR [org.kie.workbench.common.services.refactoring.backend.server.indexing.AbstractFileIndexer] (Thread-141) Unable to index 'default://master@system/datasets/tmp/e2968e11-d585-44a5-8f6c-3085c3a4436b.xlsx'.: java.lang.NullPointerException
at org.drools.decisiontable.parser.DefaultRuleSheetListener.flushRule(DefaultRuleSheetListener.java:306)
at org.drools.decisiontable.parser.DefaultRuleSheetListener.finishSheet(DefaultRuleSheetListener.java:286)

'