Can a fillet be drawn between a line and a spline curve?

I have a shallow curve that was drawn as a spline though points. I have a line cutting across the end of that curve. If I attempt to draw a fillet at the intersection I cannot select the spline curve. Should this curve be converted into something else first? And if so, what and how. Or any other solutions welcome :)

Thank you.

Sadly, this is not possible in LibreCAD yet.
A spline has very complex math which is not implemented. So all kind of tools which need to find intersections or tangents with splines don't work.
Most applies to ellipses and elliptical arcs too, they also do not support all tools.

You have to use lines or arcs for the fillet tool. So you need an approximation of the spline build from circular arcs. Sadly LibreCAD has no tool for this too.

An option in LibreCAD is to save the drawing in R12 format. The older DXF R12 format has no SPLINE or ELLIPSE entities and thus these entities are converted to polylines when saved. But it's not an arc approximation, splines or ellipses are converted to a small, straight line segments in R12.
You can give it a try, when you save the drawing under a new name in DXF R12 and then reopen it.
For printing or as a stencil, this may be sufficient. But if you want to do any kind of machining, you should first try if the converted spline works fine.

Armin

Thank you Armin for your very informative reply. I tried saving in R12 but as this is to be a laser cut item and I was still having trouble getting a fillet in, I decided on a work around.

This is a part for a small model boat so although I want parts to fit well this part is not supercritical. It's a shallow curve so I trimmed the spline (divide) back 3mm from the crossing line where I needed to fillet. Drew a straight line from the end of the spline to the end of the crossing line where it originally joined. Then put my 2.5mm R fillet on those two straight lines. That .5mm straight that's left is visually undetectable.

My apologies if that's a little crude.