Currently, there are no tools to edit and manipulate with attributes. You can access it via Python, though:

The script is looks like this:

import bmesh
import bpy

me = bpy.context.object.data
bm = bmesh.from_edit_mesh(me)

# this line works only in edit mode:
bm = bmesh.from_edit_mesh(me)

ea = bm.edges.layers.float['CustomEdgeAtr']

# set some edges:
bm.edges[1][ea]=1
bm.edges[3][ea]=1
bm.edges[4][ea]=1
bm.edges[5][ea]=1
bm.edges[6][ea]=1
bm.edges[7][ea]=1

bmesh.update_edit_mesh(me)

Currently, there are no tools to edit and manipulate with attributes. You can access it via Python, though:

The script looks like this:

import bmesh
import bpy

me = bpy.context.object.data
bm = bmesh.from_edit_mesh(me)

# this line works only in edit mode:
bm = bmesh.from_edit_mesh(me)

ea = bm.edges.layers.float['CustomEdgeAtr']

# set some edges:
bm.edges[1][ea]=1
bm.edges[3][ea]=1
bm.edges[4][ea]=1
bm.edges[5][ea]=1
bm.edges[6][ea]=1
bm.edges[7][ea]=1

bmesh.update_edit_mesh(me)