Unify hovertemplate title cannot be edited.

Hello

It seems that we cannot modify the title of the hovertemplate when the chart uses a unify hovermode whenever the axis has not a date type.

Here a short example with 2 scatter plots, the first one with a date axis and the second is linear:

import numpy as np
import pandas as pd
from plotly.subplots import make_subplots

dates = pd.date_range("2022-01-01", "2022-03-01")
values = np.random.randint(0, 10, len(dates))

fig = make_subplots(cols=2) 
fig.add_scatter(x=dates, y=values, row=1, col=1)
fig.add_scatter(x=values, y=values, mode="markers", row=1, col=2)

fig.update_traces(hovertemplate="%{y}<extra></extra>")
fig.update_xaxes(row=1, col=1, hoverformat=" ")
fig.update_xaxes(row=1, col=2, type="linear", hoverformat=" ")
fig.update_layout(hovermode="x unified")

fig.show()

If you force the second scatter to be a date type, the hovertemplate title is removed with the workaround hoverformat=" ". However, it only works for date axis.

Here some references/related issues:
https://github.com/plotly/plotly.py/issues/4278
https://community.plotly.com/t/customizing-text-on-x-unified-hovering/39440/18
https://community.plotly.com/t/pass-nothing-or-disable-x-axis-hoverformat/67496

plotly version = 5.18.0

Exécutez la reproduction Python fournie avec plotly 5.18.0 et comparez les cas date-axis et linear-axis. Lisez l’issue associée #4278 et les discussions communautaires liées ; le travail est considéré comme terminé lorsque unified hover sur un linear axis permet de supprimer ou de personnaliser le titre de hovertemplate sans imposer un date axis, avec une couverture de régression.