Got a recording from tvlatas, which shows that values longer than ~258 chars (or maybe it's a pixel limation) is not displayed in the JFR ui.

The full string is
weblogic.rmi.internal.activation.ActivatableCollocatedRef - hostID: '-3521580764875341143S:192.168.211.37:slcn04i:3000,slcn05i:3006,slcn06i:3000,slcn04i:3006,slcn05i:3012,slcn06i:3006,slcn04i:3012,slcn05i:3018,slcn06i:3012,slcn04i:3018,slcn05i:3024,slcn06i:3024,slcn04i:3024,slcn05i:3030,slcn06i:3030,slcn04i:3030,slcn05i:3036,slcn06i:3036,slcn04i:3036,slcn05i:3042,slcn06i:3042,slcn04i:3042,slcn05i:3048,slcn06i:3048,slcn04i:3048,slcn05i:3054,slcn06i:3054,slcn04i:3054,slcn05i:3060,slcn06i:3060:XA_f34d190a-8e60-48eb-93ba-dfcf9682bdaa_Domain:c1_slcn04iServer10 channel: 'null' aid 463651301675262635

Table displays:
weblogic.rmi.internal.activation.ActivatableCollocatedRef - hostID: '-3521580764875341143S:192.168.211.37:slcn04i:3000,slcn05i:3006,slcn06i:3000,slcn04i:3006,slcn05i:3012,slcn06i:3006,slcn04i:3012,slcn05i:3018,slcn06i:3012,slcn04i:3018,slcn05i:3024,slcn06i:30

Tooltip displays a few more, maybe because it's not bold?weblogic.rmi.internal.activation.ActivatableCollocatedRef - hostID: '-3521580764875341143S:192.168.211.37:slcn04i:3000,slcn05i:3006,slcn06i:3000,slcn04i:3006,slcn05i:3012,slcn06i:3006,slcn04i:3012,slcn05i:3018,slcn06i:3012,slcn04i:3018,slcn05i:3024,slcn06i:3024,slcn04i:3024,s

Only way to get the full value (if you know it differs from the displayed) is to copy and paste it into a text editor.

Could this be an SWT limitation?

In the case it lead the user to understandaly believe that there was something wrong with the grouping mechanisms.

See T:\klara\jfr\wls\2017_01_26_07_03_16_8732_0.jfr and event type MyProfiler->Remoteref->RemoteRefGetOutBoundBefore for repro.