Currently, it is not possible to copy to clipboard cell values from tables or from text widgets. This is a very useful feature present in Qlikview. There is a threat in the community with workarounds and there are certain extensions with this feature, however it would be much better if this came out-of-the-box.
This would be awesome in the native product. So many times I want to quickly copy and paste a value and I have to go through the process of exporting to Excel.
The plugin that someone tried to create for Chrome does not work either.
From the current information and status on the feature request, this should be targeted in one of the next Qlik Sense versions (copy to cell value to clipboard - for tables).