A short-term solution that may work is to do
http://localhost:5000?value=test
then
from flask import request
@app.route("/")
def index():
urlParamValue = request.args.get('value')
# Retrieve the script to include the bokeh app to the page.
script = server_document('http://localhost:5006/bokeh_app', arguments={"value": urlParamValue})
return render_template("app.html", script=script, resources=CDN.render())