Please try to provide minimal info required to reproduce the issue when producing a testcase. Regarding your case, just wrap your output in <span> block.
import '../_shared/shared.js'; // not required, our example styling etc.
import Grid from '../../lib/Grid/view/Grid.js';
new Grid({
appendTo : 'container',
minHeight : '20em',
rowHeight : 200,
columns : [
{
text : 'Action',
field : 'f5',
width : 100,
htmlEncode : false
}
],
data : [
{
f5 : '<span>Type new interface transaction into Display field<br/><b>[Details]</b><br/>Type new interface transaction description into Description field<br/><b>[Details2]</b><br/>Leave 0 in Sequence field</span>'
}
]
});